Angular relation and energy dependence of Andreev reflection

Benistant, P A M; Gelder, A. P. van; Kempen, H. van; Wyder, P.

doi:10.1103/physrevb.32.3351

Cited by 55 publications

(20 citation statements)

References 11 publications

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“…Due to a small energy loss of the electron due to its condensation into a Cooper pair, the holes energy and in-plane momentum, and hence its angle of reflection, are in all generality smaller than that of the incident electron. This effect is exceedingly small in typical metallic systems where E F strongly exceeds typical energies of , and perfect retro-AR in these systems has been confirmed in great detail [3].…”

Section: Introductionmentioning

confidence: 68%

Crossover from retro to specular Andreev reflections in bilayer graphene

Efetov¹,

Efetov²

2016

Phys. Rev. B

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Ongoing experimental progress in the preparation of ultraclean graphene/superconductor (SC) interfaces enabled the recent observation of specular interband Andreev reflections (ARs) at bilayer graphene (BLG)/NbSe 2 van der Waals interfaces [Efetov et al., Nat. Phys. 12, 328 (2016)]. Motivated by this experiment we theoretically study the differential conductance across a BLG/SC interface at the continuous transition from high to ultralow Fermi energies E F in BLG. Using the Bogoliubov-de Gennes equations and the Blonder-Tinkham-Klapwijk formalism we derive analytical expressions for the differential conductance across the BLG/SC interface. We find a characteristic signature of the crossover from intraband retro (high E F ) to interband specular (low E F ) ARs that manifests itself in a strongly suppressed interfacial conductance when the excitation energy |ε| = |E F | < (the SC gap). The sharpness of these conductance dips is strongly dependent on the size of the potential step at the BLG/SC interface U 0 .

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Section: Introductionmentioning

confidence: 68%

Crossover from retro to specular Andreev reflections in bilayer graphene

Efetov¹,

Efetov²

2016

Phys. Rev. B

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“…The current-carrying states in high magnetic fields are edge states at the 2D EG boundary with Fermi energy E F . The edge states with Landau level index n (referred to collectively äs an edge channel) can only be transmitted across a potential barrier if their guiding center energy (6) exceeds the potential-barrier height (disregarding tunneling through the barrier). Here a> c =eB/m is the cyclotron frequency, and the Zeeman spin Splitting is ignored for simplicity.…”

Section: Transition To the Quantum Hall Regimementioning

confidence: 99%

“…The focusing action of a magnetic field can then be detected in an elegant way by usmg a second point contact, which acts äs a collector or voltage probe (drawmg no net current). This technique, pioneered by Sharvm 1 and Tsoi, 2 is a powerful tool to obtain Information on the shape of the Fermi surface, 3 on electron-phonon interaction, 4 and on surface scattenng The surface can be a free surface of a crystal, 5 or a metal-superconductor mterface 6 (Andreev reflection 7 ) In metals, electron focusing is essentially a classical transport phenomenon, because of the small Fermi wavelength λ^ (typically 0.5 nm)…”

Section: Introductionmentioning

confidence: 99%

Coherent electron focusing with quantum point contacts in a two-dimensional electron gas

et al. 1989

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Transverse electron focusing in a two-dimensional electron gas is mvestigated expenmentally and theoretically for the flrst time. A split Schottky gate on top of a GaAs-Al x Ga,_^As heterostructure defines two point contacts of variable width, which are used äs mjector and collector of ballistic electrons As evidenced by their quantized conductance, these are quantum point contacts with a width comparable to the Fermi wavelength At low magnetic flelds, skipping orbits at the electrongas boundary are directly observed, thereby establishing that boundary scattenng is highly specular Large additional oscillatory structure in the focusing spectra is observed at low temperatures and for small pomt-contact size This new phenomenon is mterpreted in terms of mterference of coherently excited magnetic edge states m a two-dimensional electron gas A theory for this effect is given, and the relation with nonlocal resistance measurements in quantum ballistic transport is discussed It is pomted out, and expenmentally demonstrated, that four-termmal transport measurements m the electron-focusmg geometry constitute a determmation of either a generalized longitudmal resistance or a Hall resistance At high magnetic fields the electron-focusmg peaks are suppressed, and a transition is observed to the quantum Hall regime The anomalous quantum Hall effect m this geometry is discussed m light of a four-termmal resistance formula

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“…A very important physical process in this respect is the Andreev reflection, 15 whereby an electron incident on a superconductor-normal interface is ͑partially͒ retroreflected as a hole into the normal conductor and a Cooper pair is created in the superconductor. The first direct experimental observation of the peculiar property of the Andreev reflection, i.e., that all velocity components are reversed, was achieved by Benistant et al 2,3 using the versatile tool of transverse electron focusing ͑TEF͒. 16 The experimental and theoretical investigation of the two-dimensional electron gas using the TEF technique has been pioneered by van Houten et al 17 ͑see also a recent review 18 discussing these experiments in terms of coherent electron optics͒.…”

Section: Introductionmentioning

confidence: 98%

Andreev edge channels and magnetic focusing in normal-superconductor systems: A semiclassical analysis

et al. 2007

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We study a transverse electron-hole focusing effect in a normal-superconductor system. The spectrum of the quasiparticles is calculated both quantum mechanically and in semiclassical approximation, showing an excellent agreement. A semiclassical conductance formula is derived, which takes into account the effect of electronlike as well as holelike quasiparticles. At weak magnetic fields, the semiclassical conductance shows characteristic oscillations due to the Andreev reflection, while for stronger fields it goes to zero. These findings are in line with the results of previous quantum calculations and with the expectations based on the classical dynamics of the quasiparticles.

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Angular relation and energy dependence of Andreev reflection

Cited by 55 publications

References 11 publications

Crossover from retro to specular Andreev reflections in bilayer graphene

Crossover from retro to specular Andreev reflections in bilayer graphene

Coherent electron focusing with quantum point contacts in a two-dimensional electron gas

Andreev edge channels and magnetic focusing in normal-superconductor systems: A semiclassical analysis

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